1. Field of the Invention
This invention relates to a cleaning agent for hard, particularly metallic, surfaces. It thus represents a so-called industrial cleaning agent, particularly a so-called neutral cleaning agent. Because of its particular combination of glycol ethers and cationic surfactants it is low-foaming and may therefore preferably be used as a spray cleaning agent over the entire temperature range of about 15 to about 80.degree. C. relevant to the technical applications.
2. Discussion of Related Art
Such industrial cleaning agents are chiefly used in the car industry and its support industries for cleaning and passivating predominantly in spray cleaning units. They are suitable for the intermediate and final cleaning of components machined by cutting and non-cutting methods in body and assembly shops. Vitually all relevant materials, such as iron and steel, aluminum, silumin, copper, brass, zinc and plastics, may be treated and the majority of all organic or inorganic-based contaminants, such as cooling lubricants, rust prevention oils, machining oils, drawing auxiliary substances, pigments and light metal dust, may be removed. Such cleaning agents may also be used in conventional dip processes, although the use thereof in the spray process is conventionally preferred.
The chemical base components of such industrial cleaning agents are conventionally surfactants and organic corrosion inhibitors. The latter ensure temporary corrosion protection during and after treatment. In addition, such cleaning agents generally contain substances which are capable of counteracting undesirable foaming. In most cases, the use of such foam-inhibiting additives is called for because the impurities which are detached from the substrates and build up in the cleaning baths act as foaming agents.
Furthermore, the use of so-called foam inhibitors may also be required because of the fact that the cleaning agents themselves contain constituents which may give rise to undesirable foaming under the specified working conditions, i.e. particularly in the case of spray processes, such as anionic surfactants or non-ionic surfactants which foam at the working temperature in question.
The use of fatty alcohol polyethylene glycol ethers, also known as fatty alcohol ethoxylates, as the surfactant component in washing and cleaning agents is known from "Ullmanns Encyklopadie der technischen Chemie", 4th edition, vol. 22 (1982), pages 489 to 493. Such addition products of ethylene oxide to fatty alcohols are not, however, suitable for use in spray processes alone as they foam considerably at application temperatures of from 15 to 80.degree. C. It is also known to use fatty alcohol ethyoxylate/ propoxylates as low-foaming wash raw materials; cf. the above-mentioned Ullmann volume, page 494, for example.
DE-A-36 20 011 describes cationic surfactants based on quaternary ammonium compounds and the use thereof in cleaning agents. The cationic surfactants are used in the alkaline pH range in addition to further cleaning agent constituents.
EP-A-0 116 151 describes a process for regenerating and/or recycling aqueous degreasing and cleaning solutions by addition of cationic surfactants or cationically modified polymers or mixtures thereof.
EP-A-0 054 895 describes a surfactant mixture of a non-ionic surfactant and a quaternary ammonium compound as cationic surfactant for cleaning hard surfaces. In the mixture the non-ionic surfactant content is 20 to 95 wt. %, that of the cationic surfactant 5 to 80 wt. %.
DE-A-40 14 859 describes a low-foaming surfactant combination for cleaning hard surfaces which comprises at least one quaternary ammonium compound as well as at least one alkyl polyethylene glycol mixed ether. These mixed ethers have either one acyclic alkyl or alkenyl group having 6 to 18 carbon atoms or one cyclic alkyl group having 5 or 6 carbon atoms. This surfactant combination may additionally contain alkyl ethoxylates or alkyl ethoxylate/propoxylates which have one alkyl or alkenyl group having 6 to 18 carbon atoms in each case.
A cleaning agent for gas turbine compressors which contains 4 to 95 wt. % of glycol ether, 0.1 to 14 wt. % of nonionic-surfactant, 0.01 to 6 wt. % of cationic surfactant and 0 to 95 wt. % of water is known from EP-A-275 987. EP-A-691 397 discloses an anti-microbial cleaning agent for hard surfaces which contains as solvent C.sub.1-6 -alkanol-C.sub.3-24 -alkylene glycol ethers, amphoteric and/or non-ionic surfactants, cationic surfactants, builders and water. DE-C-41 02 709 proposes an agent for degreasing metal surfaces which contains 15 to 30 wt. % of adducts of low alkylene oxides to fatty alcohols having turbidity points below 50.degree. C., 0.5 to 3 wt. % of cationic surfactants and 10 to 20 wt. % of auxiliary solvents from the group of the C.sub.2-5 alkanols and low glycol ethers in water.
Accordingly, agents are known which contain fatty alcohol ethoxylates, cationic surfactants and low glycols as solvents or solubilizers. The basis of the invention is the surprising finding that, with suitable combination of glycols and cationic surfactants, an outstanding cleaning effect is achieved without these agents additionally containing amphoteric surfactants or fatty alcohol alkoxylates which act like surfactants, such as ethoxylates or propoxylates. In this case, fatty alcohol alkoxylates are to be understood to mean alkoxylates of alcohols having at least 6 carbon atoms in the alkyl group according to the disclosure of EP-A-691 397.
In the application concentration of about 0.5 to about 5 wt. %, all sprayable surfactant systems exhibit a range of disadvantages:
1 . To ensure low-foaming, application takes place above the so-called turbidity point. The application solutions are accordingly rendered turbid by means of a dispersed, surfactant-rich phase. This surfactant-rich phase is easily separated off by means of conventional measures to prolong service life, such as skimmers, separators, centrifuges or membrane filtration, and is no longer available for the cleaning process. PA1 2. The conventional non-ionic surfactant systems, such as fatty alcohol or fatty amine ethoxylates or propoxylates and the mixed ethers thereof are classified in water hazard class 2. PA1 3. The non-ionic surfactants having good degreasing action, such as fatty alcohol ethoxylates having more than 4 moles of ethylene oxide or fatty amine ethoxylates having more than 5 moles of ethylene oxide, which do not have a turbidity point at the conventional application temperatures, foam to an extremely high degree and are not considered alone for spray applications, Rather, foam inhibitors, which make little or no contribution to the cleaning performance, must be added. To incorporate these foam inhibitors into the liquid cleaning agent concentrates, solubilizers, so-called hydrotropic substances, are often required in order to obtain clear concentrates. These solubilizers represent a further ballast which does not itself contribute towards the cleaning performance. PA1 (a) glycol ethers corresponding to the general formula: EQU R--O--(CH.sub.2 --CH(CH.sub.3)O).sub.n --H, PA1 wherein R represents an alkyl group having 1 to 4 carbon atoms or a phenyl group; and n represents a number of from 1 to 5; and PA1 (b) cationic surfactants; PA1 R.sup.1 represents a straight or branched alkyl group having 1 to 22 carbon atoms; PA1 R.sup.2 may represent hydrogen or a straight or branched alkyl group having 1 to 22 carbon atoms; the total number of carbon atoms in the groups R.sup.1 and R.sup.2 being from 10 to 22; PA1 n=0 or 1; PA1 R.sup.3 and R.sup.4 independently represent methyl, ethyl, 2-hydroxyethyl or hydroxypropyl; PA1 R.sup.5 represents alkyl groups having 1 to 12 carbon atoms, a benzyl group or alkylphenyl groups having 1 to 3 carbon atoms in the alkyl group; and wherein the total number of carbon atoms of the quaternary ammonium cation is at least 9 and at least one of the groups R.sup.1 and R.sup.5 has more than 4 carbon atoms; and PA1 X.sup.- represents halide, methyl sulfate or an anion of an aliphatic or aromatic organic acid having up to 15 carbon atoms.
In contrast, an object of the invention is to provide a new substance combination with effective cleaning action which does not have the above-mentioned disadvantages. In particular, a new substance combination having active cleaning action is to be provided which provides clear, low-foaming and sprayable cleaning solutions in the temperature range of about 15 to about 80.degree. C. which is relevant in practice, without needing additional foam inhibitors and solubilizers for this purpose.